I went to camp for the first time after having Astarion wait there instead of join my party on the road (Also after finding an animal drained of blood).
My party was attacked at camp and I knocked him unconscious. The BUG is when I then went to sleep and the whole Astarion wants to suck my blood thing happens... EXCEPT Astarion is actually replaced by my Custom Character and in the place of my Custom Character is Shadowheart on the bedroll.
... it was an odd experience lol.